The product tab is only visible to users with Administrative privileges
Once in the Products menu, click the Purchasing drop down menu.
Click the Purchase Order button.
Click the + button above the product list.
Shipping Info Tab:
Fill in the information as needed.
From the drop down menu, selecting the Vendor.
Select the Product.
Click the + to add the product to the list.
Edit the product information as needed.
Repeat as needed.